1. Field of the Invention
The present invention relates to a recording medium determination apparatus and an image forming apparatus. In particular, the present invention relates to a recording medium determination apparatus that detects a surface smoothness of a recording medium to determine the recording medium and an image forming apparatus such as an ink jet printer, a copying machine, or a laser printer that controls image conditions to the determined recording medium.
2. Description of the Related Art
Conventionally, an image forming apparatus (e.g., copying machine, laser printer) includes: a latent image bearing member for supporting a latent image; a development apparatus for adding developer to the latent image bearing member to visualize a latent image as a developer image; and a transfer mechanism for transferring a developer image by the development apparatus onto a recording medium transferred in a specified direction. The image forming apparatus also includes a fixing apparatus that fixes a developer image on a recording medium by heating and pressurizing the recording medium on which the developer image is transferred by the transfer mechanism based on specified fixing processing conditions.
Conventionally, such an image forming apparatus has been structured as described below. When the size or type of a recording medium is set by a user through an operation panel or the like provided in the image forming apparatus body for example, a control is performed to change, depending on this setting, a development condition, a transfer condition, or a fixing processing condition or an image processing. It is noted that the type of a recording medium also may be hereinafter referred to as a paper type. Fixing processing condition includes, for example, a fixing temperature or a transport speed of a recording medium passing through the fixing apparatus. When a user sets a paper type for a printing operation through a host computer, the image forming apparatus performs a control to change, depending on the set paper type, a development condition, a transfer condition, a fixing processing condition, or an image processing.
The image forming apparatus forms a surface image of a recording medium by a complementary metal-oxide semiconductor (CMOS) sensor. A technique has been disclosed by Japanese Patent Laid-Open No. 2002-182518 for example. This technique introduces, with regards to the surface image, the maximum density pixel Dmax, the minimum density pixel Dmin, and a contrast that is a difference between Dmax and Dmin to use this contrast to determine the type of the recording medium. Depending on the type of the recording medium thus determined, the image forming apparatus subjects a development condition, a transfer condition, or a fixing condition to a variable control.
Another apparatus has been suggested in which a light-emitting source is provided at a position opposed to a sensor for determining a recording medium to detect transmitted light to determine a recording medium based on the transmitted light.
However, the above-described conventional recording medium determination apparatus, which calculates the surface smoothness based on the difference in contrast among pixels of an obtained image of the recording medium to determine the recording medium, may not accurately extract the feature of the recording medium to result in an erroneous determination. Furthermore, the conventional recording medium determination apparatus requires a long time for the determination (e.g., acquisition of a corrected image) in order to remove the light intensity variation of a light irradiation mechanism or noise in an obtained image. Thus, the conventional technique has left some problems unsolved.